Wheel bearing device

ABSTRACT

A wheel bearing device includes a hub ring, a double-row bearing and a constant velocity universal joint which are unitized together. At least one of double-row inner raceways of the bearing and a wheel mounting flange are formed on a hub ring. The hub ring and a stem portion of a joint outer ring of the constant velocity universal joint are fitted through a torque transmission assembly, wherein a pilot member as a separate element having a wheel guide portion and a brake guide portion is fitted to a side-end portion of the wheel mounting flange of the hub ring, and the hub ring and the pilot member are fixed to the joint outer ring by swaging.

CROSS REFERENCE TO RELATED APPLICATION

This is a Divisional Application which claims the benefit of U.S. patentapplication Ser. No. 10/771,394, filed Feb. 5, 2004, which issued asU.S. Pat. No. 7,232,374 on Jun. 19, 2007, which is a Divisional of U.S.application Ser. No. 09/956,465, filed Sep. 20, 2001, which issued asU.S. Pat. No. 6,739,977 on May 25, 2004. The disclosures of the priorapplications, now patents, are hereby incorporated herein in theirentirety by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a wheel bearing device which rotatably supportsa wheel of an automobile on an car body.

2. Description of the Related Art

A wheel bearing device (hereinafter referred to as “bearing device”)shown in FIG. 45 is for a driving wheel and has a constitution in whicha hub ring 1, a bearing 2, and a constant velocity universal joint 3 areunitized.

The hub ring 1 is provided with an outboard inner raceway 4 on its outerperipheral surface as well as a wheel mounting flange 6 for mounting awheel (not shown). Hub bolts 7 for fixing a wheel disc are studded onthe wheel mounting flange 6 with equal intervals in a circumferentialdirection. A pilot portion 40 having a wheel guide portion 38 and abrake guide portion 39 is unitizedly formed with an outboard end portionof the hub ring 1. Also, a brake rotor (not shown) is mounted on thewheel mounting flange 6 together with the wheel disc.

The constant velocity universal joint 3 is provided at an end of a shaft8 and comprises a joint outer ring 11 with a track groove 9 formed onits inside periphery, a joint inner ring 12 having a track groove 10formed on its outside periphery opposing the track groove 9 of the jointouter ring 11, torque transmission balls 13 installed between the trackgroove 9 of the joint outer ring 11 and the track groove 10 of the jointouter ring 11, and a cage 14 supporting the torque transmission balls 13disposed between the joint outer ring 11 and the joint inner ring 12.Between the joint outer ring 11 and the shaft 8 is a boot 15 forpreventing entry of water and foreign matter from outside and leakage ofgrease contained inside.

The joint outer ring 11 has a mouse portion 16 storing the joint innerring 12, the torque transmission balls 13 and the cage 14, and a stemportion 19 axially extending from the mouse portion 16, with a serratedportion 17 being formed thereon. Transmission of torque from the stemportion 19 to the hub ring 1 is enabled by inserting the stem portion 19into a through-hole of the hub ring 1 so that they are fit each otherthrough serrated portions 17 and 18 formed respectively on an outsideperipheral surface of the stem portion 19 and an inside peripheralsurface of the through-hole. An axial end of the joint outer ring 11 isplastically deformed to be roll-formed to an outboard end portion of thehub ring 1, and the joint outer ring 11 is fixed to the hub ring 1 by aroll-formed portion 20.

Double-row inner raceways are formed with an outboard inner-raceway 4formed on an outer peripheral surface of the hub ring 1 and with aninboard inner-raceway 5 formed on an outer peripheral surface of ashoulder portion 21 of the joint outer ring 11. The joint outer ring 11is inserted into the hub ring 1 axially from the inboard side and isroll-formed to the hub ring 1. Thereby a shoulder portion 21 of thejoint outer ring 11 butts against an inboard end portion of the hub ring1, thereby pre-load is applied to the bearing 2.

The bearing 2 is of a double-row angular ball bearing constitution, andis constituted such that rolling elements 25 and 26 are disposed betweenthe inner raceways 4 and 5 formed respectively on outer peripheralsurfaces of the hub ring 1 and joint outer ring 11 and outer raceways 23and 24 formed respectively on an outer ring 22, and the rolling elements25 and 26 of each row are supported by cages 27 and 28 at equalintervals in a circumferential direction. The outer ring 22 is providedwith an car-body mounting flange 29 for mounting an car body (not shown)on it. The car-body mounting flange 29 is fixed with bolts on a knuckleextending from a suspension device (not shown) of the car body. Atopening portion at both ends of the bearing 2, a pair of seals 30 and 31sealing an annular space formed by the outer ring 22, the hub ring 1 andthe joint outer ring 11 are fitted into inner peripheral portions at endportions of the outer ring 22 to prevent inside grease from leaking andwater and foreign matter from entering from outside. The seals 30 and 31are provided with seal lips that are in sliding contact onto outerperipheral portions of the hub ring 1 and the joint outer ring 11.

While the bearing device shown in FIG. 45 is a type having anon-separable constitution in which the hub ring 1, the bearing 2 andthe constant velocity universal joint 3 are unitized together, FIGS. 46and 47 show other examples of bearing devices of a type having aseparable constitution in which a hub ring 1′ and the bearing 2 areunitized together, and the constant velocity universal joint 3 is fixedto the hub ring 1′ with bolts 32 or nuts 33. A separable type differsfrom a non-separable type as described below.

An inner ring 35, a separate element from the hub ring 1′, is fittedonto a small-diameter end portion 34 formed on an outside periphery ofan inboard end portion of the hub ring 1′, and an inboard inner raceway5 is formed on an outside periphery of the inner ring 35. The inner ring35 is pressed into position with an appropriate interference to preventcreeping from occurring. Both an outboard inner raceway 4 formed on anoutside periphery of the hub ring 1′ and the inboard inner raceway 5formed on the outside periphery of the inner ring 35 form double-rowinner raceways. The inner ring 35 is pressed onto the end portion of thesmall-diameter portion 34 of the hub ring 1′, the end portion of thesmall-diameter portion 34 of the hub ring 1′ is outwardly roll-formed byplastically deforming it, and the roll-formed portion 36 serves toprevent the inner ring 35 from loosening and coming off, and to applypre-load to the bearing 2.

In this type of bearing devices, because of the constitution in whichthe roll-formed portion 36 serves for the prevention of coming off andapplication of pre-load, the joint outer ring 11 is fixed to the hubring 1 in the following way: a stem portion 19 of the joint outer ring11 is inserted into the through-hole of the hub ring 1′, then the jointouter ring 11 is fixed to the hub ring 1′ with tightening torquenecessary and sufficient to prevent the joint outer ring 11 fromloosening from the hub ring 1′ either by engaging a bolt 32 into athreaded hole 37 formed on a stem portion 19 of the joint outer ring 11(see FIG. 46) or by engaging a nut 33 onto the stem portion 19 of theouter joint ring 11 (see FIG. 47).

The bearing device in FIG. 45 is constituted such that the stem portion19 of the joint outer ring 11 is roll-formed by plastically deformingit, and the joint outer ring 11 is fixed to the hub ring 1 by aroll-formed portion 20. Therefore, considering the convenience inassembly of this bearing device, a serration fit between the hub ring 1and the stem portion 19 of the joint outer ring 11 is preferably loose.

Also, in the bearing devices in FIG. 46 and FIG. 47, the roll-formedportion 36 of the hub ring 1′ serves to prevent the inner ring 35 fromloosening and coming off, and to apply pre-load to the bearing 2, andthe bolt 32 or the nut 33 fixes the constant velocity universal joint 3to the hub ring 1′. Because the swaged portion 36 of the hub ring 1′serves to prevent the inner ring 35 from loosening and apply pre-load tothe bearing 2 as described above, applying pre-load by fastening torqueof the bolt 32 or the nut 33 becomes unnecessary, and the bolt 32 or thenut 33 fixes the joint outer ring 11 to the hub ring 1′ with fasteningtorque that is necessary and sufficient to prevent the joint outer ring11 from loosening.

However, when the serration fit between the hub ring 1 or 1′ and thestem portion 19 is loose for convenience in assembly of the bearingdevice, play may occur between the serrated portions 17 and 18 of thehub ring 1 or 1′ and the stem portion 19 respectively, resulting inpossible deterioration in drive feeling and generation of an unusualsound in a driving system. Also, a constitution of this type is weak tomoment load applied to the hub ring 1, an attempt for securingsufficient strength for the stem portion 19 and the roll-formed portion20 hinders the miniaturization of the entire device.

Also, because the bearing devices in FIGS. 45 to 47 are constituted suchthat the stem portion 19 of the joint outer ring 11 is fitted into aninside periphery of the hub ring 1 or 1′, the dimensions in a radialdirection of the serrated portions 17 and 18 for torque transmissioncannot be made larger than the inside diameter of the hub ring 1 or 1′.When the diameters of serrated portions cannot be made larger asdescribed above, the serrated portions inevitably have to be made longerin an axial direction to secure a predetermined transmitted torque,which results in inconvenience in that the dimension in the axialdirection of the bearing device increases.

In the bearing device in FIG. 45, specifically, moment load acting onthe hub ring 1 is received mainly only by the outboard bearing 2 of thedouble row bearing 2. This is because the hub ring 1 and the joint outerring 11 tend to be bent at their butted portion when moment load isapplied, so that an inboard bearing is not capable enough to supportmoment load. Therefore, excessive force may cause looseness at theroll-formed portion 20, so that lack in coupling strength between thehub ring 1 and the outer joint ring 11, as well as lack in strength ofthe stem portion 19 of the joint outer ring 11 is feared.

Also, in the bearing devices in FIGS. 45 to 47, because the innerraceway 4 is formed on the hub ring 1 or 1′, and the hub ring 1 or 1′has a function equivalent to a raceway of a general roller bearing, thehub ring 1 or 1′ must be made of steel for bearing in the same way as araceway of such a general roller bearing. However, because steel forbearing is extremely purified steel, it is expensive. Also, steel forbearing contains a higher amount of carbon for hardenability and forhardness on a raceway surface, so that it has low ductility, which leadsin poor workability in forging.

In a wheel bearing device, generally, an inboard bearing is subjected toseverer load conditions than an outboard bearing. Conventionally,specifications of internal parts of both inboard and outboard bearingshave been made equal without considering such a point described above.Briefly, the pitch circle diameters and other dimensions of outboard andinboard bearings have been made equivalent. This means, however, that anoutboard outer raceway 23 also inevitably has a large radius dimensionthat satisfies the rated load of an inboard bearing, which is againstdemand for miniaturization and weight-reduction of a bearing device.Furthermore, when designing a bearing device, it must be considered thata hub bolts 7 do not contact with an outer ring 22 in case of repair,for example, in the case when the hub bolt 7 is drawn from wheelmounting flange 6; however, a larger radial dimension of the outboardouter raceway 23 makes such consideration difficult to realize,restricting the freedom in design. Consequently, the design itself of abearing device cannot be realized in an extreme case.

In a bearing device in FIG. 45, a axial end of the joint outer ring 11is plastically deformed to roll-form it to an outboard end portion ofthe hub ring 1, and the joint outer ring 11 is fixed to the hub ring 1by the roll-formed portion 20. Therefore, during the roll-formingoperation, run-out occurs on the wheel mounting flange 6 of the hub ring1. Run-out of the flange will cause face run-out (or run-out in an axialdirection) on a brake rotor to be mounted on the wheel mounting flange 6of the hub ring 1, causing vibration in braking while the automobile istraveling at a high speed or resulting in a problem such as uneven wearof the brake rotor or brake juddering.

Generally, in view of the reason of easiness in forging, workability incold forging, and machinability or because of economy, rawun-heat-treated medium carbon steel (S53C and others) for machinestructural purpose is used for the hub ring 1. Miniaturization andweight-lightening of a bearing device greatly contribute for increasedtravel stability of an automobile, so that the wheel mounting flange 6of the hub ring 1 is increasingly constituted with ribs and thinned.However, such movement is bringing the mechanical strength of the hubring itself to a fatigue limit of the material, or medium-carbon steelfor machine structural purpose, and therefore, further weight-reductionis becoming difficult. Specifically, thinning of the wheel mountingflange 6 of the hub ring 1 for weight-reduction purpose can causeconcentration of rotational bending stress at an outboard base portionof the wheel mounting flange 6, or at a fillet located at a regionextending from a brake rotor mounting surface to a cylindrical pilotportion 41, and the fillet can be a starting point of breakage.

An inboard base portion of the wheel mounting flange 6 is a sealingsurface with which the seal-lip of a seal 30 is in sliding contact, andthe sealing surface has a larger curvature with a quenching-temperingtreatment being applied to give abrasion resistance on the surface.Therefore, the inboard root portion of the wheel mounting flange 6 hashigher mechanical strength than an outboard base portion that is notheat-treated, so that the inboard base portion is less likely to be astarting point of breakage caused by rotational bending stress.

Although thickening of the wheel mounting flange 6 can be a solution foravoiding such breakage described above, it is against the movement ofweight-reduction. Further, generation of stress can be eased withenlarged dimensions of the base portion, or the curvature of the baseportion, of the wheel mounting flange 6; however, the application ofthis method is limited by a possible mechanical interference between thebase portion and a brake rotor to be mounted on the wheel mountingflange 6.

Also, material can be strengthened by increasing its carbon content,adding a strengthening element such as Si (silicon) or V (vanadium) orby applying a heat treatment such as normalizing; however, workabilityof the material is affected by increased material hardness.Consequently, conventional processing methods or existing facilitiesbecome difficult to be applied, and further, adding a large amount ofstrengthening elements leads to increased material costs.

SUMMARY OF THE INVENTION

It is an object of the present invention to prevent occurrence of playbetween serrated portions of a hub ring and a joint outer ring.

To attain the above object, a bearing device according to the presentinvention comprises a hub ring, a double-row bearing and a constantvelocity universal joint, at least the hub ring and the double-rowbearing are unitized, and the hub ring and a joint outer ring of theconstant velocity universal joint are fitted to each other throughtorque transmission means and joined together by means for fastening inan axial direction. In this constitution, a clearance in the fit portionof the torque transmission means is prevented from occurring by a playprevention member.

In this bearing device, fit condition of the torque transmission meansprovided between the hub ring and the joint outer ring, which was in aloose relationship for convenience in assembling a bearing device, canbe changed to a tight relationship because clearance in the fit portionof the torque transmission means provided between the hub ring and thejoint outer ring is prevented from occurring by the play preventionelement. Thereby, occurrence of play between the serrated portions ofthe hub ring and the joint outer ring, deterioration of drive feelingand generation of unusual sound from a driving system can be preventedso that a highly reliable bearing device having high quality can beprovided.

This invention is also applicable to a bearing device having aconstitution in which a hub ring, a constant velocity universal jointand a double-row bearing are unitized, one of double-row inner racewaysof the bearing is formed on a joint outer ring of the constant velocityjoint, and an end portion of the joint outer ring is fitted onto anoutside periphery of the hub ring through torque transmission means.

In a bearing device of the invention, the play prevention member forpreventing occurrence of play in the fit portion of the torquetransmission means has an outside diameter larger than an insidediameter of a hollow portion provided in the hub ring and it is adiameter-expanding member to be pressed into the hollow portion.Pressing the diameter-expanding member into the hollow portion of thehub ring expands the hub ring from the inside toward the outside, andthereby a fit condition of the torque transmission means between the hubring and the joint outer ring can be changed to a tight one.

In a bearing device according to the invention, the hub ring and thejoint outer ring can be fitted tighter by adding a constitution in whichan end portion of the hub ring is roll-formed to be coupled with thejoint outer ring or by adding a constitution where a snap ring isinstalled at an end portion of the hub ring to couple the hub ring withthe joint outer ring.

The present invention is applicable to a constitution in which the hubring has a small-diameter end portion, an inner ring as a separateelement that forms one of double-row inner raceways of a bearing ispressed onto the small-diameter end portion, the hub ring and thebearing are unitized together by roll-forming the small-diameter endportion, and a joint outer ring is fitted into a bore of the hub ringthrough the torque transmission means.

In a bearing device according to the present invention, the playprevention member for preventing a clearance occurring in the fitportion of the torque transmission means has an outside diameter largerthan an inside diameter of the hollow portion of the joint outer ringand is a diameter-expanding member to be pressed into the hollowportion. The diameter-expanding member expands the joint outer ring fromthe inside toward the outside by pressing the diameter-expanding memberinto the hollow portion, the fit condition in the torque transmissionmeans between the hub ring and the joint outer, can be changed to atighter one.

The diameter-expanding member is preferably a rolling element for abearing. Using a rolling element as a diameter-expanding memberfacilitates the expansion of the hub ring or the joint outer ring fromthe inside toward the outside by pressing the diameter-expanding memberinto the hollow portion. A ball or a roller may be used as the rollingelement.

In a bearing device according to the present invention, a small-diameterportion having an outside diameter smaller than an inside diameter ofthe hub ring is provided at an end portion of the joint outer ring, aportion having projections and depressions is formed on an outsideperiphery of the small-diameter portion in a circumferential direction,and between an inner periphery of the hub ring and an outer periphery ofthe small-diameter portion, there is installed a ring member integrallyhaving tongue pieces elastically contacting with the portion havingprojections and depressions on the small-diameter portion and with thefit portion of the torque transmission means of the hub ring.Installation of the ring member between the hub ring and thesmall-diameter portion provides a fit condition in which the tonguepieces elastically contact with both the fit portion of the torquetransmission means of the hub ring and the portion having projectionsand depressions of the small-diameter portion, of which arrangementcreates a tight fit condition of the hub ring and the joint outer ringeven play exists in the fit portion of the torque transmission means.

It is another object of the invention to make a bearing device morecompact and to improve its rigidity against moment load.

In order to attain the object, a bearing device according to theinvention comprises a hub ring, a constant velocity universal joint anda double-row bearing, of which all are unitized, and one of double-rowinner raceways of the bearing is formed on a joint outer ring of theconstant velocity universal joint, wherein the joint outer ring isfitted onto the hub ring through torque transmission means, and the hubring and the joint outer ring are joined by plastic deformation.

By fitting the joint outer ring onto the hub ring as described above, adimension of the torque transmission means in a radial direction can bemade larger than an inside diameter of the hub ring. As a result of theenlargement in the diameter of the torque transmission means, the lengthof the torque transmission means in an axial direction can be shortenedto make the bearing device more compact.

In this case, because the hub ring becomes possible to be extended toinboard side in a bore of the joint outer ring, the double-row bearing,or both inboard and outboard bearings, can take moment load acting onthe hub ring through the extended portion, so that moment rigidity ofthe bearing device is increased. Taking moment load by the double-rowbearing reduces load on the plastically deformed portion, so thatloosening of the plastically deformed portion is surely prevented, andcoupling strength between the hub ring and the joint outer ring isstably maintained over a long period of time. In order to obtain theeffect described above, an inboard end portion of the hub ring ispreferably extended beyond an inboard inner raceway of the double-rowinner raceways.

The torque transmission means and the plastically deformed portion maybe separately disposed in an axial direction. In this case, a torquetransmission function and a function of preventing the hub ring fromloosening are available independently from each other, allowing optimumdesign of both the functions such that each of the functions can beindividually enhanced.

By providing a fit portion between the hub ring and the joint outer ringin which they are fitted without play, transmission of radial loadbetween the two are ensured and radial rigidity of the bearing device isimproved. Different embodiments may be available for the arrangements ofthe fit portion, the torque transmission means and the plasticallydeformed portion. For example, the plastically deformed portion can bedisposed in an axial direction at one side of the torque transmissionmeans and the fit portion can be disposed at the other side.

The plastically deformed portion is arranged such that, for example, anend portion of the hub ring is roll-formed for coupling with the jointouter ring. More specifically, for example, a tubular portion to beroll-formed is formed at the end portion of the hub ring, the tubularportion to be roll-formed is coupled with an end surface of the jointouter ring by plastically deforming the tubular portion to beroll-formed toward the outside of the hub ring by roll-forming or othermeans, and thus the hub ring and the joint outer ring are coupledtogether by plastic deformation.

Coupling constitutions for the hub ring and the joint outer ringinclude, besides those described above, such a constitution in which thehub ring and the joint outer ring are coupled by plastically deformingan end portion of a connection member inserted into the hub ring. Theplastically deformed portion and the torque transmission means may beseparately disposed in an axial direction, and they may also be disposedon a common part.

More specifically, for example, a portion with projections anddepressions is provided within a fit range of the hub ring and the jointouter ring, and the fit range including the portion with projections anddepression is at least partly expanded or shrunk in the diameters. Byexpanding or shrinking the diameters in the fit range, the portion withprojections and depression provided either on the hub ring or on thejoint outer ring bites into the mating member, a function of torquetransmission and a function of preventing the hub ring (or the jointouter ring) from loosening are compatible.

The diameter-expanded portion or the diameter-shrunk portion in thiscase is preferably disposed on an inboard inner raceway rather than onan outboard inner raceway. By doing so, the dimension of the joint outerring in an axial direction can be shortened, decrease in accuracy of theflange end surface of the hub ring caused by punching is avoided, andsignificant rise in costs for a heat treatment for the portion withprojections and depression is avoided.

Fitting an inner ring having an outboard inner raceway on its outsideperiphery onto the hub ring can omit an outboard inner raceway from thehub ring, and the hub ring can be made as a member having no innerraceway. Accordingly, in selecting a material for the hub ring,consideration for hardenability or the hardness of an inner racewaybecomes unnecessary. Therefore, material such as extremely purifiedsteel or high-carbon steel is not necessary to be used for the hub ring,so that production costs can be lowered. The same effect is obtainableby fitting an inner ring having an outboard inner raceway on its outsideperiphery onto the joint outer ring.

For example, the diameter of an outboard outer raceway becomes smaller{circumflex over (1)} by making the pitch-circle diameter of an outboardbearing of a double-row bearing smaller than that of an inboard bearingor {circumflex over (2)} by making the diameter of outboard rollingelements smaller than that of inboard rolling elements, and thus thediameter of the outboard outer ring can be made smaller. Therefore,lightening in weight is achieved, space for removing hub bolts issecured, and freedom in design is increased.

The constitutions of {circumflex over (1)} and {circumflex over (2)}described above are applicable not only to a bearing device for adriving wheel, but also to a bearing device for a driven wheel. That is,in a bearing device in which a hub ring and a double-row bearing areunitized, the pitch-circle diameter of an outboard bearing of thedouble-row bearing is made smaller than that of an inboard bearing orthe diameter of outboard rolling elements of the double-row bearing ismade smaller than that of inboard rolling elements.

It is still another object of the present invention to preventoccurrence of run-out of a wheel mounting flange of a hub ring.

In order to attain the object, a bearing device according to theinvention comprises a hub ring, a constant velocity universal joint anda double-row bearing which are unitized together, at least one of innerraceways of double-row inner raceways of the bearing and a wheelmounting flange are formed on the hub ring, and a stem portion of ajoint outer ring of the constant velocity universal joint is insertedinto the hub ring through torque transmission means, wherein a pilotmember, which is a separated element having a wheel guide portion and abrake guide portion, is fitted to an end portion of the wheel mountingflange of the hub ring, and the hub ring and the pilot member are fixedby roll-forming to the joint outer ring. The hub ring, the pilot memberand the joint outer ring are fixed to each other by unitizing the hubring and the pilot member by roll-forming an axial end portion of thejoint outer ring to the pilot member.

The constitution described above is applicable to a bearing devicehaving a constitution in which the other inner raceway of the double-rowbearing is formed directly on the joint outer ring of the constantvelocity universal joint. Also, the stem portion and a mouth portion ofthe joint outer ring can be constituted so as that torque can betransmitted and also can be detachably constituted. In this case,preferably, the other inner raceway of the double-row inner raceways ofthe bearing is formed directly on the stem portion of the joint outerring, and the stem portion and the mouth portion, which is a separateelement, are fitted to each other through serrated portions.

In the bearing device according to the present invention, by fitting thepilot member, which is a separate element, to an end portion of thewheel mounting flange of the hub ring, alignment of the hub ring and thejoint outer ring is made by the end portion of the wheel mounting flangeand the separate pilot member, and the pilot member and the hub ring arefixed to be unitized by roll-forming an axial end of the joint outerring. The alignment of the hub ring and the joint outer ring is madethrough the separate pilot member and the end portion of the wheelmounting flange, so that occurrence of run-out of the wheel mountingflange of the hub ring can be prevented. Further, fitting the pilotmember eases stress concentration, caused by moment load applied to thehub ring, on a roll-formed portion at the axial end.

In this bearing device, it is preferable that {circumflex over (1)} thepilot member is subjected to rust-proofing, {circumflex over (2)} thesurface thereof is hardened by a heat treatment, and {circumflex over(3)} a seal member is provided on a surface thereof with which the hubring contacts.

It is still a further object of the present invention to enhance thestrength of a hub ring while aiming at the lightening in weight withoutchanging the shape and dimensions of a wheel mounting flange and withoutincreasing a carbon content in a material or without addingstrengthening elements to a material.

In order to attain the object, a bearing device according to theinvention comprises a hub ring, a constant velocity universal joint anda double-row bearing that are unitized together, at least one of innerraceways of double-row inner raceways of the bearing and a wheelmounting flange are formed on the hub ring, and a stem portion of ajoint outer ring of the constant velocity universal joint is fitted intothe hub ring through torque transmission means, wherein asurface-hardened layer is formed at least on an outboard base portion ofthe wheel mounting flange. The base portion is preferably a filletlocated at a region extending from a brake rotor mounting surface to atubular pilot portion, and the surface-hardened layer is formed byinduction hardening.

Forming the surface-hardened layer at least on an outboard base portionof the wheel mounting flange facilitates strengthening of the outboardbase portion, which is the weakest portion for rotational bendingfatigue strength, to improve the strength for rotational bending fatiguestrength without changing the shapes and dimensions of the wheelmounting flange and without increasing a carbon content in a material oradding strengthening elements in a material, but while enabling the useof current processing methods and facilities. As a result, ribbing orthinning of the wheel mounting flange can be realized, leading inminiaturization and weight-lightening of a bearing device.

In the invention, the surface hardness of the surface-hardened layer maybe from HRC 40 through 63, preferably from HRC 58 through 63, and thedepth may be from 0.3 through 2 mm, preferably from 0.5 through 2 mm.

When the surface hardness of the surface-hardened layer is made in therange from HRC 40 through 63, or preferably from HRC 58 through 63, thehardness in of range effectively prevents breakage caused by rotationalbending fatigue, because rotational bending fatigue strengthfundamentally depends on hardness. To prevent breakage caused byrotational bending fatigue means to limit the production of cracks onthe material surface. Stress caused by rotational bending has itsmaximum value at the surface and it reduces toward inside. Therefore,the depth of the surface-hardened layer is not necessarily so deep, andthe depth from 0.3 through 2 mm, preferably from 0.5 through 2 mm, isadequate.

The hub ring is preferably made of carbon steel containing C from 0.5through 0.8 wt %. Carbon steel containing C from 0.5 through 0.8 wt %has better workability than SUJ2, high-carbon chrome steel for a bearing(containing C from 0.95 through 1.10 wt %), by a degree corresponding toits less carbon content.

The hub ring comprises the wheel mounting flange on its outsideperiphery, an outboard inner raceway of the double-row inner racewaysthereon, and a small-diameter stepped portion onto which an inner ringis pressed, with the inner ring being formed with the inboard innerraceway. The present invention is applicable to a bearing devicecomprising a hub ring having such a constitution described above.

A wheel bearing device preferably comprises a seal having a seal lipslidingly contacts with an outside periphery of the hub ring or theinner ring, and a surface-hardened layer is formed about a base portionof the wheel mounting flange with which the seal lip slidingly contacts.By forming a surface-hardened layer also about a base portion of thewheel mounting flange with which the seal lip contacts, the wheelmounting flange is further strengthened.

It is preferable that a serrated portion is formed on an internalperiphery of the hub ring and a surface-hardened layer is provided onthe serrated portion. Forming a surface-hardened layer on a serratedportion improves a wear resistance and strength, and the improvedstrength allows to shorten the effective length of the serrated portion.Here, a serrated portion implies serration or spline.

The nature, principle, and utility of the invention will become moreapparent from the following detailed description when read inconjunction with the accompanying drawings in which like parts aredesignated by like reference numerals or characters.

BRIEF EXPLANATION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a cross sectional view showing a first embodiment of a bearingdevice according to the invention;

FIG. 2 is a cross sectional view showing a state before swaging isapplied to the bearing device of the first embodiment;

FIG. 3 is a cross sectional view showing a state after swaging isapplied to the bearing device of the first embodiment;

FIG. 4 is a cross sectional view showing a second embodiment of abearing device according to the invention;

FIG. 5 is a cross sectional view showing a third embodiment of a bearingdevice according to the invention;

FIG. 6 is a cross sectional view showing a fourth embodiment of abearing device according to the invention;

FIG. 7 is a cross sectional view showing a fifth embodiment of a bearingdevice according to the invention;

FIG. 8 is a cross sectional view showing a sixth embodiment of a bearingdevice according to the invention;

FIG. 9 is a cross sectional view showing a seventh embodiment of abearing device according to the invention;

FIG. 10 is a cross sectional view showing an eighth embodiment of abearing device according to the invention;

FIG. 11 is a cross sectional view showing a ninth embodiment of abearing device according to the invention;

FIG. 12 is a cross sectional view showing a tenth embodiment of abearing device according to the invention;

FIG. 13 is a cross sectional view showing an eleventh embodiment of abearing device according to the invention;

FIG. 14 is a cross sectional view showing a twelfth embodiment of abearing device according to the invention;

FIG. 15( a) is a view seen from Z-Z line of FIGS. 15( b) and 15(c), FIG.15( b) is an enlarged cross sectional view of portion A showing a ringmember in FIG. 14, and FIG. 15( c) is an enlarged cross sectional viewof portion A showing a ring member in a thirteenth embodiment, analternative example of the twelfth embodiment in FIG. 14;

FIG. 16 is a cross sectional view showing a fourteenth embodiment of abearing device according to the invention;

FIG. 17( a) is an enlarged cross sectional view of portion B showing aring member in FIG. 16, FIG. 17( b) is an enlarged cross sectional viewof portion B showing a ring member in a fifteenth embodiment that is analternative example of the fourteenth embodiment, and FIG. 17( c) is anenlarged cross sectional view of portion B showing a ring member in asixteenth embodiment that is an alternative example of the fourteenthembodiment;

FIG. 18( a) is an enlarged cross sectional view of an essential portionshowing a ring member in a seventeenth embodiment that corresponds tothe fourteenth embodiment, FIG. 18( b) is an enlarged cross sectionalview of an essential portion showing a ring member in an eighteenthembodiment that corresponds to the fifteenth embodiment, FIG. 18( c) isan enlarged cross sectional view of an essential portion showing a ringmember in a nineteenth embodiment that corresponds to the sixteenthembodiment, and FIG. 18( d) is an enlarged cross sectional view of apart showing a ring member in a twentieth embodiment;

FIG. 19 is a cross sectional view showing a twenty-first embodiment of abearing device according to the invention;

FIG. 20 shows view X depicting the contact surfaces of the ring memberand nut in FIG. 19;

FIG. 21( a) is a perspective view of a nut in a twenty-second embodimentof a bearing device according to the invention, and FIG. 21( b) is afront view of the nut in FIG. 21( a);

FIG. 22 is a characteristics diagram of a conventional bearing device,showing the relationship between tightening torque of a bolt or nut andplay at a serrated portion;

FIG. 23 is a characteristics diagram of a bearing device according tothe invention showing the relationship between tightening torque of abolt or nut and play at a serrated portion;

FIG. 24 is a cross sectional view showing a twenty-third embodiment of abearing device according to the invention;

FIG. 25 is a cross sectional view showing a twenty-fourth embodiment ofa bearing device according to the invention;

FIG. 26 is a cross sectional view showing a twenty-fifth embodiment of abearing device according to the invention;

FIG. 27 is a cross sectional view showing a twenty-sixth embodiment of abearing device according to the invention;

FIG. 28 is a cross sectional view showing a twenty-seventh embodiment inwhich an inner ring having an inner raceway is fitted to a hub ring;

FIG. 29 is a cross sectional view showing a twenty-eighth embodiment inwhich a hub ring is expanded in its diameter for swaging to be fixed toa joint outer ring;

FIG. 30 is a cross sectional view showing a twenty-ninth embodiment inwhich a hub ring and a joint outer ring are coupled with a connectionmember;

FIG. 31 is a cross sectional view showing a thirtieth embodiment inwhich pitch-circle diameters of rolling elements and other dimensionsare made to differ from each other in inboard and outboard rows;

FIG. 32 is a cross sectional view showing a thirty-first embodiment inwhich a hub ring in FIG. 31 is expanded in its diameter for swaging tobe fixed to a joint outer ring;

FIG. 33 is a cross sectional view showing a thirty-second embodiment inwhich a hub ring is expanded in its diameter for swaging to be fixed toa joint outer ring;

FIG. 34 is a cross sectional view showing a thirty-third embodiment inwhich a hub ring is expanded in its diameter for swaging to be fixed toa joint outer ring;

FIG. 35 is a cross sectional view showing a thirty-fourth embodiment inwhich a double-row conical-roller bearing is used as a bearing shown inFIG. 29;

FIG. 36 is a cross sectional view showing a thirty-fifth embodiment inwhich a hub ring is fitted onto an outside periphery of a joint outerring for fitting them to each other by expanding and swaging;

FIG. 37 is a cross sectional view showing a thirty-sixth embodiment of abearing device according to the invention;

FIG. 38 is a cross sectional view showing a thirty-seventh embodiment ofa bearing device according to the invention;

FIG. 39 is a cross sectional view showing a thirty-eighth embodiment ofa bearing device according to the invention;

FIG. 40 is a cross sectional view showing a thirty-ninth embodiment of abearing device according to the invention;

FIG. 41 is a cross sectional view of a part showing a hub ring, a stemportion of a joint outer ring and a pilot ring, all of which are shownin FIG. 37;

FIG. 42 is a cross sectional view showing a fortieth embodiment of abearing device according to the invention;

FIG. 43 is an enlarged cross sectional view of a part showing the hubring in FIG. 42;

FIG. 44 is a cross sectional view showing a forty-first embodiment of abearing device according to the invention;

FIG. 45 is a cross sectional view showing a conventionalnon-separable-type bearing device in which a hub ring, a bearing and aconstant velocity universal joint are unitized;

FIG. 46 is a cross sectional view showing a conventional separable-typebearing device in which a hub ring and a bearing are unitized, and thehub ring is fixed with bolts to a constant velocity universal joint; and

FIG. 47 is a cross sectional view showing a conventional separable-typebearing device in which a hub ring and a bearing are unitized, and thehub ring is fixed with a nut to a constant velocity universal joint.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Bearing devices in FIGS. 1 to 4 are embodiments for constitutions of anon-separable type in which a hub ring 41, bearing 42 and a constantvelocity universal joint 43 are unitized, and an inboard inner raceway45 is formed on a joint outer ring 51. Also, bearing devices in FIGS. 5to 26 are embodiments of constitutions of a separable type in which eachof inner raceways 44 and 45 are formed respectively on a hub ring 41′and an inner ring 75, i.e., a separate element, to be unitized as abearing 42, and the constant velocity universal joint 43 is fixed to thehub ring 41′ with a bolt 72 or a nut 73.

The hub ring 41 constituting the bearing device of a first embodimentshown in FIG. 1 has an outboard inner raceway 44 formed on an outsideperiphery of the hub ring 41 and is provided with a wheel mountingflange 46 for mounting a wheel (not shown) thereon. Hub bolts 47 forfixing a wheel disc are studded at circumferentially equal intervals onthe wheel mounting flange 46. A pilot member 40 for a wheel rotor isprovided at an outboard opening portion of a through hole of the hubring 41. The pilot member 40 also serves as a cap for preventing entryof water or foreign matter from outside or leakage of grease containedinside. Lightweight galvanized steel or resin having excellent corrosionresistance is suitable as a material for the member.

The constant velocity universal joint 43 is provided at an end of ashaft 48 and comprises the joint outer ring 51 with a track groove 49formed on an inside periphery thereof, a joint inner ring 52 with atrack grove 50, which surfaces the track grove 49 of the joint outerring 51, formed on an outside periphery thereof, torque transmissionballs 53 installed between the track groove 49 of the joint outer ring51 and the track groove 50 of the joint inner ring 52, and a cage 54provided between the joint outer ring 51 and the joint inner ring 52 forsupporting the torque transmission balls 53. A boot 55 is providedbetween the joint outer ring 51 and the shaft 48 to prevent entry ofwater or foreign matter from outside and leakage of grease containedinside.

The joint outer ring 51 comprises a mouth portion 56 storing the jointinner ring 52, the balls 53 and the cage 54, and a stem portion 59integrally extending from the mouth portion 56 in an axial direction.The inboard inner raceway 45 is formed on an outside periphery of thestem portion 59. The outboard inner raceway 44 formed on an outsideperiphery of the hub ring 41 and the inboard inner raceway 45 formed onan outside periphery of the stem portion 59 constitute double-row innerraceways.

The bearing 42 is of a double-row angular ball bearing structure inwhich rolling elements 65 and 66 are provided between the inner raceways44 and 45 formed respectively on an outside periphery of the hub ring 41and on the joint outer ring 51 and the outer raceways 63 and 64 of whichboth are formed on an inside periphery of an outer ring 62, and therolling elements 65 and 66 are supported at circumferentially equalintervals by cages 67 and 68. The outer ring 62 is provided with ancar-body mounting flange 69 for mounting the bearing device onto an carbody (not shown). The car-body mounting flange 69 is fixed with bolts toa knuckle extending from a suspension device (not shown) of the carbody. At opening portions at both ends of the bearing 42, a pair ofseals 70 and 71 for sealing an annular space formed by the outer ring62, the hub ring 41 and the joint outer ring 51 are fitted in bores atend portions of the outer ring 62 in order to prevent leakage of greasecontained inside and entry of water or foreign matter from outside.

In a bearing device of this first embodiment, a small-diameter endportion 81 is formed by extending an inboard end portion of the hub ring41, a serrated portion 57 is formed on an outside periphery of thesmall-diameter end portion 81, and at the same time, a serrated portion58 is formed on an inside periphery of the stem portion 59 of the jointouter ring 51. The stem portion 59 of the joint outer ring 51 is putonto the small-diameter end portion 81 of the hub ring 41 to fit them toeach other with the serrated portions 57 and 58, which allowstransmission of torque from the joint outer ring 51 to the hub ring 41.Also, the stem portion 59 of the joint outer ring 51 is butted againstthe hub ring 41 to apply pre-load to the bearing 42.

The serrated portions 57 and 58 of the hub ring 41 and the joint outerring 51 are in a loose-fit condition in an assembling process forconvenience of assembly of a bearing device; however, with constitutionsdescribed below, they are made to be in a tight-fit condition when theassembling is completed. A hollow portion, or a through hole 83, isformed in an axial direction in the small-diameter portion 81 of the hubring 41, and a steel ball 82, which is a rolling element forbearing, ispushed into the through hole 83. For the steel ball 82, a steel ballhaving an outside diameter slightly larger than a bore diameter of thethrough hole 83 is used. By pushing the steel ball 82 in, thesmall-diameter portion 81 of the hub ring 41 is expanded by plasticdeformation from the bore diameter side toward the outside diameterside, the fit between the serrated portions 57 and 58 that has been in aloose-fit condition is brought to a tight-fit condition by expanding andswaging. Beside the steel ball 82, a diameter-expanding member such as acylindrical roller can be used for expanding the diameter of thesmall-diameter portion 81 of the hub ring 41.

Further, a quench-hardened ring 84 is put onto the small-diameterportion 81 of the hub ring 41 and secured at a bottom portion of themouth portion 56 of the joint outer ring 51, the small-diameter portion81 is plastically deformed by a conventional swaging method, and aswaged portion 85 with a conventional swaging method serves to preventthe quench-hardened ring 84 from loosening. A conventional swagingmethod is suitable for the purpose in that the swaged portion 85 with aconventional swaging method is small in size and requires less space fora jig for a swaging operation than rocking die swaging method does. Thequench-hardened ring 84 works to improve the strength of a portionswaged by a conventional swaging method and to enhance the tighteningforce of the small-diameter portion 81 through the diameter expansion bypushing the steel ball 82 in, and constitutes a diameter-expanding and-swaging portion by forming a portion with projections and depressionssuch as knurled surface on a bore surface.

Fixing together the hub ring 41 and the joint outer ring 51 by applyingboth diameter-expansion swaging and conventional swaging methods at thesame time is made as shown in FIG. 2 and FIG. 3. FIG. 2 is a statebefore the swaging, and FIG. 3 is a state after the swaging.

As shown in FIG. 2, an assembly body 87 comprising the hub ring 41, thebearing 42 and the joint outer ring 51 is positioned on a fixedlyarranged jig 86 for receiving pushing load. A projection 88 integrallyformed at the tip of the jig 86 for receiving pushing load is insertedinto the through hole 83 of the hub ring 41, and a peripheral portion ofthe through hole 83 of the hub ring 41 is placed on a receiving surface89 provided around the projection 88. By placing the peripheral portionof the through hole 83 of the hub ring 41 on the receiving surface 89, apressure receiving area for a swaging process is secured, and increasein the thickness of a pilot end surface found in a conventionalconstitution is avoided, and deformation of the wheel mounting flange isprevented.

In a state in which the quench-hardened ring 84 is put on thesmall-diameter portion 81 of the hub ring 41 and is placed at a bottomportion of the mouth portion 56 of the joint outer ring 51, the steelball 82 is placed at the through-hole opening portion of thesmall-diameter portion 81 of the hub ring 41, and on the steel ball 82is arranged a jig 90 for a conventional swaging method. The jig 90 for aconventional swaging method integrally has at its center tip portion astick-out-shaped steel ball receiving portion 91, an annular concaveportion 92 is provided outside the steel ball receiving portion 91, anda ring receiving portion 93 is provided outside the annular concaveportion 92.

By lowering the jig 90 for a conventional swaging method, the steel ball82 that contacts the steel ball receiving portion 91 is pressed into thethrough hole 83 of the hub ring 41. The steel ball 82 has an outsidediameter slightly larger than an inside diameter of the through hole 83,so that the small-diameter portion 81 of the hub ring 41 is expandedfrom an inside diameter side toward an outside diameter side by thesteel ball 82, a swaged portion produced by the diameter expansion isformed between the small-diameter portion 81 of the hub ring 41 and theknurled portion on a bore surface of the quench-hardened ring 84, andthe fit condition of serrated portions 57 and 58 that has been in aloose-fit condition becomes a tight-fit condition. When the steel ball82 is pushed into near the deepest position in the through hole 83, thering receiving portion 93 of the jig 90 for a conventional swagingmethod presses the quench-hardened ring 84, and the annular concaveportion 92 swages the small-diameter portion 81 of the hub ring 41.

When the hub ring 41 has sufficient rigidity against moment load, thesteel ball 82 pushed inside in the diameter expansion process may bedrawn outboard after the swaging. If the hub ring 41 may not havesufficient rigidity against moment load, it is so constituted that thesteel ball 82 remains in the through hole 83 of the hub ring 41 afterthe swaging, facilitating to secure enough rigidity against moment load.As described above, the steel ball 82 functions as a reinforcing memberof the hub ring 41, and it also prevents entry of water or foreignmatter from outside or leakage of grease contained inside. With regardto swaging of the small-diameter portion 81 of the hub ring 41, it isdifficult to secure a space for rocking die swaging, because insidespace of the mouth portion 56 of the joint outer ring 51 is limited.Therefore, a conventional swaging method is suitable for the purposedescribed above, which allows make the swaging portion 85 smaller.

Next, FIG. 4 shows a second embodiment, a modified example of the firstembodiment. In a bearing device of the second embodiment, a portion 57′with projections and depressions is formed by a process such as knurlingon an outside periphery of the small-diameter portion 81 of the hub ring41. The stem portion 59 of the joint outer ring 51 is fitted onto thesmall-diameter portion 81 of the hub ring 41, and the portion 57′ withprojections and depressions of the small-diameter portion 81 is made tobite into the stem portion 59 to be fitted them to each other, andthereby torque transmission from the joint outer ring 51 to the hub ring41 is enabled. For both the purposes of the torque transmission and thefixing (or maintaining bearing pre-load), a constitution is provided inwhich the outside diameter of the small-diameter portion 81 of the hubring 41 is directly fixed to a bore of the stem portion 59 of the jointouter ring 51 with diameter expansion swaging using the steel ball 82.The portion with projections and depressions may be formed on an insideperiphery of the stem portion 59 of the joint outer ring 51.

The diameter expansion swaging using the steel ball 82 may be made inthe same manner as that of the first embodiment. In an assemblingprocess, the hub ring 41 and the joint outer ring 51 are in a loose-fitcondition through the portion 57′ with projections and depressions forconvenience of assembling of a bearing device; however, when theassembling is completed, they are made to be a tight-fit condition bydiameter expansion swaging using the steel ball 82.

An annular groove 94 is formed on an outside periphery of an end portionof the small-diameter portion 81 of the hub ring 41, and a snap ring 95is fitted in the annular groove 94 for preventing the hub ring 41 fromloosening. The snap ring 95 is not necessarily required, and it can beomitted if the fixing of the hub ring 41 and the joint outer ring 51 inan axial direction can be achieved by diameter expansion swaging usingthe steel ball 82 depending on the shape of a portion with projectionsand depressions formed on an outside periphery of the small diameterportion 81 of the hub ring 41 or an inside periphery of the joint outerring 51. Without the snap ring 95, shortening a dimension in the axialdirection is realized more easily.

At the outboard opening portion of the through hole 83 of the hub ring41, a cap 96 made of light weight galvanized steel or resin both ofwhich are excellent in corrosion resistance is installed for preventingentry of muddy water from outside or leakage of grease contained inside.A pilot portion 97 having a wheel guide portion and a brake guideportion is integrally formed at an outboard end portion of the hub ring41; however, a constitution with the separate pilot member 40 (seeFIG. 1) presented in the first embodiment may substitute this.

FIG. 5 shows a third embodiment in which a bearing device is of a typeseparable by removing a bolt. In this bearing device of a thirdembodiment, an inner ring 75, a separate element from a hub ring 41′, isfitted onto a small-diameter portion 74 provided at the inboard side endof the hub ring 41′, and an inboard inner raceway 45 is formed on anoutside periphery of the inner ring 75. The inner ring 75 is pressedinto position with an appropriate interference to prevent creeping fromoccurring. An outboard inner raceway 44 formed on an outside peripheryof the hub ring 41′ and the inboard inner raceway 45 formed on theoutside periphery of the inner ring 75 constitute double-row innerraceways. The inner ring 75 is pressed onto the small-diameter endportion 74 of the hub ring 41′, a projected end portion of thesmall-diameter end portion 74 of the hub ring 41′ is roll-formed throughplastic deformation at a roll-formed portion 76 outwardly, and theroll-formed portion 76 serves to prevent the inner ring 75 fromloosening, and to apply pre-load to the bearing 42.

The joint outer ring 51 comprises the mouth portion 56 storing the jointinner ring 52, the ball 53 and the cage 54, and the stem portion 59,integrally extending in an axial direction from the mouth portion 56,with the serrated portion 57 being formed thereon. The stem portion 59is inserted into the through hole of the hub ring 41′, and by fittingthem to each other with the serrated portion 57 and 58 formedrespectively on an outside periphery of the stem portion 59 and on aninside periphery of the through hole, transmission of torque from thestem portion 59 to the hub ring 41′ is enabled. The stem portion 59 ofthe joint outer ring 51 is inserted through the through hole of the hubring 41′, a bolt 72 is engaged in a threaded hole 77 formed in the stemportion 59, and thereby the joint outer ring 51 is fixed to the hub ring41′. Because the roll-formed portion 76 of the hub ring 41′ serves toprevent loosening of the inner ring 75 and apply pre-load to the bearing42, tightening torque of the bolt 72 is set at a level that is necessaryand sufficient for preventing the joint outer ring 51 from looseningfrom the hub ring 41′.

In this third embodiment, a hollow portion, or the through hole 83, isformed in the stem portion 59 of the joint outer ring 51, and the steelball 82 having the outside diameter slightly larger than the insidediameter of the through hole 83 is pushed into the through hole 83 froma bottom side of the mouth portion 56. Pushing in of the steel ball 82expands the stem portion 59 from the inside diameter side toward theoutside diameter side, and this diameter expansion makes a fit conditionbetween the serrated portion 57 and 58, which has been in a loose-fitcondition, a tight-fit condition, and at the same time, pilot portions57″ and 58″ formed respectively on an outside periphery of the stemportion 59 and on an inside periphery of the through hole 83 are alsofitted with the diameter expansion. A plug 98 can be screwed in at anopening of a mouth portion of the through hole 83 for preventing thesteel ball 82 from loosening; however, the plug 98 may not be installedfor easiness of disassembling the hub ring 41′ and the bearing 42 fromthe constant velocity universal joint 43.

The diameter expansion by using the steel ball 82 may be made in thesame manner as that of the first and the second embodiments. Theserrated portions 57 and 58 of the hub ring 41′ and the joint outer ring51 are in a loose-fit condition in an assembling process for convenienceof assembling of a bearing device; however, when the assembling iscompleted they are brought to a tight-fit condition by diameterexpansion using the steel ball 82. The hub ring 41′ is plasticallydeformed in the diameter expansion swaging in the first and secondembodiments, however, in the third embodiment, diameter expansionswaging is made within the range of elastic deformation of the stemportion 59. By doing so, the steel ball 82 is pushed out toward inboardside in disassembling, and the serrated portions 57 and 58 respectivelyof the hub ring 41′ and the stem portion 59 can be returned to aloose-fit condition, making disassembly easier.

A bearing device of a fourth embodiment is shown in FIG. 6. The fourthembodiment differs from the third embodiment as described below. In thethird embodiment, the plug 98 is screwed in at the opening of the mouthportion of the through hole 83 to prevent loosening of the steel ball82, while in the fourth embodiment, an end cap 99 made of steel isfitted at the opening of the mouth portion of the through hole 83. Withthis constitution, the end cap 99 serves to prevent loosening of thesteel ball 82 and leakage of grease, and disassembly is also madeeasier.

FIG. 7 shows a bearing device of a fifth embodiment. In the fifthembodiment, a hollow portion 83′ is formed at an outboard end portion ofthe stem portion 59 of the joint outer ring 51, and the joint outer ring51 is fixed to the hub ring 41′ by engaging a bolt 72 into the threadedhole 77 formed at a bottom portion of the hollow portion 83′. Aquench-hardened ring 100 is installed at a base portion of the bolt 72,the quench-hardened ring 100 is pushed in by tightening the bolt 72 toexpand the stem portion 59 from an inside diameter side toward theoutside diameter side within the range of elastic deformation, and thereby a fit condition between the serrated portions 57 and 58 that has beenin a loose-fit condition is brought to a tight-fit condition by thediameter expansion swaging.

A ring 100′ may be unitized with the bolt 72 as a sixth embodiment shownin FIG. 8. Also, it may be so constituted that a cage 101 is usedinstead of the ring as a seventh embodiment shown in FIG. 9, and thestem portion 59 is expanded from the inside diameter side within therange of elastic deformation toward the outside diameter side bytightening the bolt 72 to push in a plurality of steel ball 82′ disposedat circumferentially equal intervals with the cage 101. Further, it maybe so constituted that a ring 102 with a cross section having a circulararc is installed on the bolt 72 as shown in an eighth embodiment in FIG.10, an inside diameter of a through hole to which the ring 102 arccontacts is made to be a tapered receiving surface 103 of which diametershrinks from the outboard side toward the inboard side, the ring 102 arcis pushed in by tightening the bolt 72 to expand the stem portion 59 isexpanded from the inside diameter side within the range of elasticdeformation toward the outside diameter side.

Next, a bearing device of a ninth embodiment is shown in the FIG. 11. Inthe ninth embodiment, the threaded hole 77 is formed at an outboard endportion of the through hole 83 of the stem portion 59, and a taperedportion 104 connecting through to the threaded hole 77 is formed. Thetapered portion 104 has a bore of which diameter shrinks from theoutboard side having a diameter substantially equal to the outsidediameter of the steel ball 82 toward the inboard side having a diametersmaller than the outside diameter of the steel ball 82. By tighteningthe bolt 72, the steel ball 82 is pushed into the tapered portion 104 ofthe through hole 83 from the outboard side toward inboard side, the boreof the stem portion 59 is expanded in the range of elastic deformationtoward the outside diameter side, and by this diameter expansionswaging, a fit condition between the serrated portions 57 and 58 thathas been in a loose-fit condition is brought to a tight-fit condition.

FIG. 12 shows a bearing device of a tenth embodiment. The tenthembodiment differs from the ninth embodiment such that described below.Instead of providing a tapered bore portion connected through to thethreaded hole 77 in the through hole 83 of the stem portion 59, astraight bore portion having a diameter slightly smaller than theoutside diameter of the steel ball 82 is provided in the through hole83, and an end cap 105 that serves to prevent loosening of the steelball 82 and leakage of grease is installed. In the tenth embodiment, bypushing out the steel ball together with end cap 105 in disassembling,the serrated portion 57 and 58 of the hub ring 41′ and the stem portion59 are allowed to return to a loose-fit condition, so that thedisassembly is carried out easier.

FIG. 13 shows a bearing device of an eleventh embodiment. In theeleventh embodiment, a tubular member 106 for applying pre-load to thebearing 42 is fitted to the hub ring 41′ through serrated portions 57 aand 58 a and is swaged to be fixed in position by plastically deformingan outboard end portion of the hub ring 41′. A serrated portion 57 b isformed on an outside periphery of the outboard end portion of a jointouter ring 51′, a serrated portion 58 b is formed on a bore surface ofan large-diameter inboard end portion of the tubular member 106, and byfitting the joint outer ring 51′ and the tubular member 106 to eachother through the serrated portions 57 b and 58 b, transmission oftorque from the joint outer ring 51′ to the hub ring 41′ is enabled. Abolt 72′ inserted through the tubular member 106 is engaged with thejoint outer ring 51′ at a threaded hole 77′ and the cage 101 is storedin an annular space formed between the inboard end portion of the bolt72′ and the joint outer ring 51′.

In the eleventh embodiment, the hub ring 41′ and the joint outer ring51′ are joined and unitized together by tightening the bolt 72′ via thetubular member 106, and the joint outer ring 51′ is, through thetightening of the bolt 72′, expanded from the inside diameter sidetoward the outside diameter side in the range of elastic deformation bypressing and securing in position a plurality of the steel ball 82′disposed at circumferentially equal intervals by the cage. Thus, a fitcondition between the serrated portions 57 b and 58 b that has been in aloose-fit condition is made to be a tight-fit condition. Indisassembling, the steel balls 82′ in the cage 101 is released from thepressed-in state by removing the bolt 72′, the fit condition of theserrated portions 57 b and 58 b of the joint outer ring 51′ and thetubular member 106 can be returned to a loose-fit condition.

Next, FIG. 14 is a twelfth embodiment showing a bearing device, a typeseparable by removing a nut. In the twelfth embodiment, a small-diameterportion 107 has a diameter smaller than that of a part on which theserrated portion 57 fitting to the serrated portion 58 of the hub ring41′ is formed. The small-diameter portion 107 is integrally provided onthe stem portion 59 of the joint outer ring 51, a portion withprojections and depressions, or a serrated portion 108, for example, isformed on the outside periphery of the small-diameter portion 107, andas shown in FIGS. 15( a) and 15(b), a ring member 109 made of steel isinstalled between the serrated portion 108 on the small-diameter portion107 and the serrated portion 58 on the hub ring 41′. The ring member 109is such that a plurality of tongue pieces 110 having a shape curvedtoward the inside diameter side are arranged at the outboard sidethereof at circumferentially equal intervals, and a plurality of tonguepieces 111 having a shape curved toward the outside diameter side aredisposed at the inboard side thereof at circumferentially equalintervals. The ring member 109 is quench-hardened.

By pressing the ring member 109 into between the serrated portion 108 onthe small-diameter portion 107 of the stem portion 59 and the serratedportion 58 on the hub ring 41′, the tongue pieces 110 and 111 areengaged and coupled with both the serrated portions 108 and 58, therebyplay between the serrations 57 and 58 respectively of the stem portion59 and the hub ring 41′ is prevented. As a thirteenth embodiment shownin FIG. 15( c), when the ring member 109′ is made in a shape so that itsoutboard side is extended in an axial direction to contact with an endsurface of the nut 73, the end surface of the nut 73 can press the ringmember 109′ into the inboard side when the nut 73 is tightened, whichfacilitates the pressing of the ring member 109′ into between theserrated portion 108 on the small-diameter portion 107 of the stemportion 59 and the serrated portion 58 on the hub ring 41′.

FIG. 16 and FIG. 17 (a) show a fourteenth embodiment, a modified exampleof the twelfth and thirteenth embodiments. In the thirteenth embodiment,the ring member 109′ is pressed and fixed by tightening the nut 73,while in a bearing device of the fourteenth embodiment, the ring member109″ is pressed and fixed by a circlip 112 installed on the axial end ofthe stem portion 59 of the joint outer ring 51. A curved press-downportion 113 is integrally and extendedly provided at an outboard endportion of the ring member 109″, and the ring member 109″ is pressedinto position through the press-down portion 113 when the circlip 112 isinstalled.

Also, as a fifteenth embodiment shown in FIG. 17( b), when, ininstalling the circlip 112, the press-down portion 113 of the ringmember 109″ is compressed in an axial direction and fixed in position inan elastically deformed state, movement of the stem portion 59 of thejoint outer ring 51 in an axial direction can be prevented. Further, ina constitution in which an elastic member 114 such as a rubber is storedand held in the press-down portion 113 of the ring member 109″ as asixteenth embodiment shown in FIG. 17( c), the press-down portion 113 ofthe ring member 109″ is compressed in an axial direction and fixed inposition in an elastically deformed state in the same manner as in thefifteenth embodiment, and thus the elastic member 114 makes theinstallation of the circlip easier.

In the embodiments from the fourteenth to sixteenth, the ring member109″ is fixed by the circlip 112 considering convenience fordisassembling; however, as shown by the embodiments from seventeenth tonineteenth in FIGS. 18( a)-18(c), it may also be so constituted that, agroove 115 with sharp bottom corners is formed on an outside peripheryof the stem portion 59 instead of using the circlip 112, and an endportion of the press-down portion 113 of the ring member 109″ is engagedand coupled with the groove 115 with sharp bottom corners.

Each of the embodiments from the seventeenth to the nineteenth shown inFIGS. 18( a) to 18(c) corresponds to each of the embodiments from thefourteenth to the sixteenth shown in FIGS. 17( a) to 17(c). As shown ina twentieth embodiment in FIG. 18( d), the constitution may also be suchthat an end portion of the press-down portion 113 of the ring member109″ is of a shape that inclines toward its axis so that it can beengaged and coupled with the groove 115 with sharp bottom corners on thestem portion 59. Also, by providing slits at parts indicated by arrowsin FIGS. 18( a) to 18(c), the press-down portion 113 on the ring member109″ is more easily engaged and coupled with the groove 115 having sharpbottom corners on the stem portion 59, and thereby workability ininstalling the ring member 109″ is improved.

FIG. 19 is a twenty-first embodiment of a bearing device. In thetwenty-first embodiment, as shown in FIG. 20, fine teeth 117 and 118that lock the nut 73 against a loosening direction are formed on anoutboard end surface of a ring member 116 press-fitted in advance intothe through hole of the hub ring 41′ and on the end surface of the nut73 that engages with the stem portion 59.

In the twenty-first embodiment, play between the serrated portions 57and 58, respectively of the stem portion 59 and the hub ring 41′, can beprevented by tightening the nut 73 through the ring member 116, and atthe same time, the teeth 117 and 118 biting each other between the nut73 and the ring member 116 also realizes prevention for loosening thenut 73. The ring member 116 may be either of sintered material or steel.Also, it may be constituted in such a way that, as shown in atwenty-second embodiment in FIGS. 21( a) and 21(b), a nut 73′ is ofsteel, brim portions 120 raised toward the ring-plate side are formed ona seat surface 119 of the nut 73′, and the brim portions 120 are engagedand coupled with the teeth 117 of the ring member 116.

With regard to play between the serrated portions 57 and 58 of the stemportion 59 and the hub ring 41′ with respect to tightening torqueapplied either by a bolt or a nut, FIG. 22 shows characteristics of aconventional constitution and FIG. 23 shows those of a constitutionaccording to the invention. Comparing both characteristics, it isobviously understood that, in a constitution according to the invention,play between the serrated portions 57 and 58 of the stem portion 59 andthe hub ring 41′ is more controlled in a constitution of the inventionthan a conventional constitution.

In a bearing device of a separable type in which the hub ring 41′ andthe bearing 42 are unitized and the constant velocity universal joint 43is fixed to the hub ring 41′ with a nut, the inboard end portion of thehub ring 41′ is roll-formed as described above, and the roll-formedportion 76 prevents loosening of the inner ring 75 and applies pre-loadto the bearing 42, in which the center position of the constant velocityuniversal joint 43 is shifted toward the inboard side by the amount ofthickness dimension of the swaged portion 76. That is, in afont-wheel-drive front-wheel-steer vehicle, aligning the center positionof the constant velocity universal joint 43 and the center position of akingpin becomes difficult, which spoils freedom in design.

A bearing device of a twenty-third embodiment shown in FIG. 24 presentsmeans to minimize the shift of the center position of the constantvelocity universal joint 43 caused by the roll-formed portion 76 of thehub ring 41′. The number of torque transmission balls installed betweenthe joint outer ring and joint inner ring of a constant velocityuniversal joint is generally six, while in the twenty-third embodiment,eight pieces of the torque transmission balls are installed between thejoint outer ring 51 and joint inner ring 52 of the constant velocityuniversal joint 43. Using eight pieces of torque transmission balls 53′allows to make the outside diameter of each torque transmission ball 53′smaller, and the dimension of the constant velocity universal joint 43in an axial direction can be shortened by the reduced diameterdimension, so that the shift of the center position of the constantvelocity universal joint 43 can be minimized.

As other means to minimize the shift of the center position of theconstant velocity universal joint, a twenty-fourth embodiment shown inFIG. 25 or a twenty-fifth embodiment shown in FIG. 26 are presented. Inthe twenty-fourth and twenty-fifth embodiments, a diameter of an innerring 75′ is made larger by increasing the thickness of the inner ring75′ of the bearing 42 in a radial direction, thereby the pitch circlediameter (PCD) of inboard rolling elements 66′ is made larger than thatof the outboard rolling elements 65 to shorten a ball pitch distanceuntil an installation span is equal. By doing so, the inboard rollingelements 66′ can be moved to the outboard side, so that the dimension ofthe constant velocity universal joint 43 in the axial direction can beshortened by the dimension moved, minimizing the shift of the centerposition of the constant velocity universal joint 43. The outsidediameter of the inboard rolling elements 66′ may be made smaller thanthat of the outboard rolling elements.

In a twenty-fourth embodiment shown in FIG. 25, an annular space 121 ata concave portion is provided in a part at the joint outer ring 51 withwhich the roll-formed portion 76 contacts, and the roll-formed portion76 of the hub ring 41′ is stored in the space 121 at a concave portion.Further, in a twenty-fifth embodiment shown in FIG. 26, because thethickness in a radial direction of the inner ring 75′ becomes thicker, aconcave portion 122 is formed on the inboard end portion of the innerring 75′, and the roll-formed portion 76 of the hub ring 41′ is storedin the concave space 121 of the joint outer ring 51 and in the concaveportion 122 of the inner ring 75′. With the constitution describedabove, the length in an axial direction of the constant velocityuniversal joint 43 can be shortened, and thereby the shift of the centerposition of the constant velocity universal joint 43 can be minimized.In the constitutions described above, an outside circumferential portionaround the concave space of the joint outer ring 51 is made to contactwith an inboard end portion 123 of the inner ring 75′, and therebymoment load applied to the bearing can be supported, and the rigidity ofthe entire unit is enhanced.

A bearing device shown as a twenty-sixth embodiment in FIG. 27 is for adriving wheel, and a shaft-shaped portion 145 having a fitting surface144 on its outside periphery is formed at a position more inboard sidethan the flange 46 of the hub ring 41. The inboard end portion of theshaft-shaped portion 145 is extended to a position beyond the inboardinner raceway 45. A solid-shaped hub ring is shown in the figure as anexample of the hub ring 41; however, it may be a hollow-shaped for aweight-lightening purpose.

The joint outer ring 51 is composed of the mouth portion 56 formed withthe track groove 49 on its inside periphery, and the hollow stem portion59 extending toward the outboard side of the mouth portion 56. The stemportion 59 is provided with the inboard inner raceway 45 on an outsideperiphery near the mouth portion 56. A tubular fit surface 147 is formedon an inside periphery at the outboard end portion of the stem portion59.

In the twenty sixth embodiment, an inner ring 146 is fitted and fixed onan outside periphery of the joint outer ring 51. The inner ring 146 isprovided with the outboard inner raceway 44 on its outside periphery andis pressed onto an outside periphery of the outboard end portion of thestem portion 59 with an interference that is necessary and sufficient toprevent creeping from occurring.

The joint outer ring 51 is fitted onto an outside periphery of theshaft-shaped portion 145 of the hub ring 41 with the inner ring 146being pressed and fixed onto an outside periphery of the stem portion59. At this time, by engaging the serrated portion 57 formed on anoutside periphery of the shaft-shaped portion 145 of the hub ring 41with serrated portion 58 formed on an inside periphery of the stemportion 59 of the joint outer ring 51, torque transmission is madebetween the joint outer ring 51 and the hub ring 41 through the serratedportions 57 and 58.

On the outboard side of the serrated portions 57 and 58, a fit portion148 is formed in which the fit surface 147 of the joint outer ring 51and the fit surface 144 of the hub ring 41 are fitted to each other. Inthe fit portion 148, because the fit surfaces 144 and 147 are fitted toeach other without play with an interference fit, radial load issecurely transmitted between the hub ring 41 and the joint outer ring51, thereby radial rigidity of the bearing is increased.

As described above, when a tubular end portion (or a portion to beswaged) of the hub ring 41 projecting in the mouth portion 56 isplastically deformed toward outside diameter side by using means such asrocking die swaging after the joint outer ring 51 is fitted onto the hubring 41, a swaged portion 149, a plastically deformed portion coupleswith an end portion of the joint outer ring 51, pushes the joint outerring 51 into the outboard side. As a result, a front surface of theinner ring 146 contacts with a shoulder surface 150 formed on the stemportion 59 of the joint outer ring 51, a back surface of the inner ring146 contacts with a surface extending in a radial direction of the hubring 41, the hub ring 41 and the joint outer ring 51 are positioned inan axial direction, so that the dimension between the inner raceways 44and 45 is defined, and at the same time, pre-load is applied to thebearing 42.

In the twenty-sixth embodiment shown in FIG. 27, the joint outer ring 51is fitted onto the hub ring 41 as described above. Therefore, thedimensions of the serrated portions in a radial direction are notlimited to under the bore diameter dimension of the hub ring 41, and thediameters of the serrated portions 57 and 58 can be enlarged. Thisallows to shorten the lengths in an axial direction of the serratedportions 57 and 58, and to make a bearing device more compact in size.

Also, because an inboard end portion of the hub ring 41 is extendedbeyond the position of the inboard inner raceway 45, moment load from awheel acting on the hub ring 41 can be supported not only by theoutboard bearing, but also by the inboard bearing. Because moment loadis supported by a double-row bearing as described above, problems suchas insufficient rigidity of the hub ring 41, loosening at the swagedportion 149 and the like, which occur in a bearing device that supportsmoment load mainly by an outboard bearing, are not involved, and momentrigidity of the entire bearing device is improved.

In a bearing device in which an outboard inner raceway is formed on ahub ring, the hub ring functions itself as a raceway of a commonrolling-element bearing. Therefore, the hub ring is made of expensivesteel for bearing, or extremely purified steel, and particularly ofhigh-carbon steel advantageous for securing hardenability and hardnessof a raceway surface, which significantly raises material costs.Additionally, in a constitution that requires swaging of an end portionof the hub ring, because of characteristics of high-carbon steel, theportion to be swaged must be treated with annealing or thermal refiningfor easier swaging operation, which also raises production costs.

Contrary to this, in the twenty-sixth embodiment shown in FIG. 27, theoutboard inner raceway 44 is formed on the inner ring 146, a separateelement from the hub ring 41, and neither of the outboard inner raceway44 nor the inboard inner raceway 45 is provided on the hub ring 41.Therefore, no consideration is required for hardenability or thehardness of the inner raceway in selecting material for the hub ring 41,and extremely purified steel or high-carbon steel is not necessary to beused. As a result, steel material containing carbon in a degree similarto that of steel for normal use may be used as a material of the hubring 41 to prevent material costs from rising. Also, steel of low- tomedium-carbon content such as S15C to S50C (preferably S45C) as definedin JIS (Japanese Industrial Standards) may be used to lower the hardnessof the portion to be swaged so that workability in swaging operation isimproved. In this case, an appropriate thermal refining treatment may beapplied to the steel material to improve its characteristics such asfatigue strength and others. Addition of boron in the material furtherimproves fatigue strength after thermal refining. Even when a thermalrefining treatment is not applied, addition of an element such asvanadium improves the fatigue strength of a material.

FIG. 28 shows a twenty-seventh embodiment, which differs from theembodiment in FIG. 27 in that the inner ring 146 is fitted onto anoutside periphery of the hub ring 41 and is butted with an end portionof the joint outer ring 51. In this case, the inner ring 146 ispositioned by making the front surface of the inner ring 146 to contactwith an end portion of the joint outer ring 51 and making the backsurface of the inner ring 146 to contact with a surface of the hub ring41 extending in a radial direction. In this embodiment, because the stemportion 59 of the joint outer ring 51 is fitted onto the shaft-shapedportion 145 of the hub ring 41 through the serrated portions 57 and 58,shortening in the dimension in an axial direction of the serratedportions 57 and 58 is achieved by enlarging the diameters, and momentrigidity is improved by supporting moment load with a double-rowbearing. Also, because the hub ring 41 is not provided with an innerraceway, the hub ring 41 is not necessary formed with steel forbearing,so that production costs are reduced.

A twenty-eighth embodiment in FIG. 29 shows a modified example of thecoupling constitution of the hub ring 41 and the joint outer ring 51, inwhich the inner ring 146 is fitted onto the outside periphery of the hubring 41 in the same manner as the embodiment shown in FIG. 28, a portion151 with projections and depressions is provided (the range where theportion 151 with projections and depressions is provided is indicatedwith ‘x’ marks) in a fit region of the hub ring 41 and the joint outerring 51, the fit region of the hub ring 41 and the joint outer ring 51including the portion 151 with projections and depressions is partlyapplied with diameter expansion (or diameter shrinkage) to plasticallycouple the hub ring 41 and the joint outer ring 51 with each other. FIG.29 shows an example in which the hub ring 41 formed in a hollow shape ispartly applied with diameter expansion, however, they may also beplastically coupled by partly shrinking the diameter of the joint outerring 51 with the portion 151 with projections and depressions beinginvolved.

In this joining constitution, because the diameter of the hub ring 41 isexpanded (or the diameter of the joint outer ring is shrunk), theportion 151 with projections and depressions bites into the matingsurface, so that the hub ring 41 and the joint outer ring 51 are jointin a state in which torque transmission is possible, and a solidcoupling constitution is provided which will not loosen even under anexcessive moment load. The joining constitution provides the serratedportion 57 and 58, and the swaged portion 149, shown in FIG. 27 and FIG.28, on a common part, and it allows to make the dimension in an axialdirection of a bearing device shorter than a case in which the serratedportions 57 and 58 are independently formed.

The portion 151 with projections and depressions may be made in anyshape. For example, it may be a knurled surface or may be teeth thatextend in an axial direction (such as serration or spline) formed on aplurality of places in a circumferential direction. Also, the portion151 with projections and depressions is preferably hardened with a heattreatment so that it has excellent bite-in capability for coupling. Whenthe portion 151 with projections and depressions is hardened asdescribed above and is used on an element of which diameter is expandedor shrunk, the portion 151 with projections and depressions may crackduring swaging as the diameter is expanded or shrunk. Therefore, theportion 151 with projections and depressions is preferably formed on amember that is not subjected to diameter expansion (or diameter shrunk),or for example, formed on an inside periphery of the joint outer ring 51of this embodiment.

In the twenty-eighth embodiment in FIG. 29, an example of a constitutionis shown, in which a snap ring 152 fitted to the inboard end portion ofthe hub ring 41 is couple with an end surface of the joint outer ring 51for strengthening a loosening prevention function; however, the snapring may be omitted if conditions allow (see FIG. 33 to FIG. 35).Further, FIG. 29 shows an example in which the inner ring 146 is fittedonto an outside periphery of the hub ring 41; however, the inner ring146 may be fitted onto an outside periphery of the joint outer ring 51in the same manner as the embodiment shown in FIG. 27.

The hub ring 41 and the joint outer ring 51 may be joined each other inthe joining constitution shown in FIG. 30. In a twenty-ninth embodimentin FIG. 30, the hub ring 41 is formed in a hollow shape, one end portionof a connection member 153 fitted into an inside periphery of the hollowshape is roll-formed and plastically deformed. As shown in the figure, acoupling portion 154 is formed at the other end of the connection member153, one end of the connection member 153 is roll-formed while makingthe coupling portion 154 couple with the joint outer ring 51, theroll-formed portion 149 produced by the roll-forming is coupled with thehub ring 41, and thereby the hub ring 41 and the joint outer ring 51 aresurely joined. The same effect as described above is also obtainablewhen the direction of the connection member 153 is reversed from thatshown in the figure to couple the coupling portion 154 with the hub ring41, and the roll-formed portion 149 is coupled with the joint outer ring51.

In FIG. 30, the outboard inner raceway 44 is directly formed on the hubring 41; however, it may be so constituted that the inner raceway 44 isformed on the inner ring 146, a separate element from the hub ring 41,and the inner ring 146 is fitted onto an outside periphery of the hubring 41 or the joint outer ring 51.

A thirtieth embodiment in FIG. 31 is for a driving wheel, in which thejoint outer ring 51 is fitted onto the hub ring 41 in the same manner asthe embodiments shown in FIG. 27 to FIG. 30. In the embodiment shown inFIG. 30, in contrast to a bearing device in which specifications of anoutboard bearing are made to accord with those of an inboard bearinghaving tougher load conditions than the outboard bearing, the diameterof the outboard rolling elements 65 is made smaller than that of theinboard rolling elements and the pitch circle diameter of the outboardbearing is made smaller than that of the inboard bearing. By doing so,the dimension in a radial direction of the outboard outer raceway 63becomes smaller, enabling lightening the weight of the bearing device.Also, the outside diameter of the outer ring 62 at the outboard side canbe made smaller than that at the inboard side, a space for removing hubbolts 47 is easily secured and freedom in design is improved.

In this case, both the pitch circle diameter and the diameter of therolling elements in the outboard side bearing are made smaller; however,the same effect is obtained when either the pitch circle diameter of thebearing or the diameter of the rolling elements is made smaller at theoutboard side bearing, and the diameter not made smaller is made equalto that of the inboard side bearing. FIG. 31 shows an example in whichthe outboard inner raceway 44 is formed on an outside periphery of thehub ring 41 in the same manner as the embodiment shown in FIG. 30.However, the inner ring 146 having the outboard inner raceway 44 may befitted onto the outside periphery of the joint outer ring 51 in the samemanner as the embodiment shown in FIG. 27 to FIG. 29.

In the thirtieth embodiment shown in FIG. 31, an end surface of the stemportion 59 of the joint outer ring 51 is made to contact with theshoulder portion 150 of the hub ring 41, the inboard end portion of thehub ring 41 is swaged, the swaged portion 149 is made to couple with anend portion of the joint outer ring 51, and thereby the hub ring 41 andthe joint outer ring 51 are plastically joined. The joining constitutionfor joining the hub ring 41 and the joint outer ring 51 may be made inany form. For example, as a thirty-first embodiment shows in FIG. 32,the hub ring 41 and the joint outer ring 51 may be plastically joined bypartly expanding or shrinking the diameters in a fit region with theportion 151 having projections and depressions being provided in the fitregion of the hub ring 41 and the joint outer ring 51. Also, although afigure is not shown, the connection member 153 may be used toplastically join the hub ring 41 and the joint outer ring 51 in the samemanner as shown in FIG. 30.

The constitution described above in which different dimensions are givento the pitch circle diameters or the rolling-element diameters atinboard and outboard sides is applicable not only to a bearing devicefor a driving wheel, but also to that for a driven wheel (not shown). Ina bearing device for a driven wheel, the hub ring 41 and the double-rowbearing 42 are unitized, and the constitution is different from that ofa driving wheel shown in FIG. 27 to FIG. 32 in that the constantvelocity universal joint 43 is not provided in a bearing device for adriven wheel. In this kind of a bearing device for driven wheels, theoutboard inner raceway 44 is generally formed on an outside periphery ofthe hub ring 41, and the inboard inner raceway 45 is formed on an innerring fitted onto an outside periphery of the hub ring 41. As describedwith reference to FIG. 29, if the hub ring 41′ is fitted onto an outsideperiphery of the joint outer ring 51′ as a thirty-fifth embodiment inFIG. 36 at the time when the hub ring 41 and the joint outer ring 51 areplastically joined by diameter expansion swaging (or diameter shrinkageswaging), a plastically deformed portion 149′ produced by swaging isinevitably disposed at more outboard side than the outboard innerraceway 44′, creating the following problems:

{circumflex over (1)} The joint outer ring 51′ becomes longer in anaxial direction, which is against demands for weight-lightening,

{circumflex over (2)} Diameter expansion swaging is made by pushing apunch 155 into an inside periphery of the hub ring 41′. The push-in mustbe made in the direction in which the joint outer ring 51′ and the hubring 41′ couple with each other in an axial direction so that pre-loadis given. In this case, push-in load must be received by a jig 156disposed at an outboard end surface of the wheel mounting flange 46′ ofthe hub ring 41′; however, accuracy in run-out of an end-surface of thewheel mounting flange 46′ may be affected.

{circumflex over (3)} As described above, in diameter expansion swaging,a portion 151′ with projections and depressions is preferably formed onan element at the outer side, or on an inside periphery of the hub ring41′, and the portion is hardened by a heat treatment. In this case, heattreatment of the hub ring 41′ must be applied to both an outsideperiphery including the inner raceway 44′ and an inside peripheryincluding the portion 151′ with projections and depressions, and therebyheat-treatment costs are increased.

Contrary to this, when the joint outer ring 51 is fitted onto an outsideperiphery of the hub ring 41 as shown in FIG. 29, the region of diameterexpansion can be disposed at more inboard side than the outboard innerraceway 44. As a result, the joint outer ring 51 may be shortened inlength in an axial direction, the weight is lightened and processingcosts (costs of such as forging and machining) are reduced. Diameterexpansion swaging can be made by inserting a punch from the outboardside. Therefore, push-in load can be received by an end surface 51 a ora bottom 51 b of the mouth portion 56 of the joint outer ring 51, sothat affect to run-out accuracy of an end surface of the wheel mountingflange 46 is avoided. Further, because the portion 151 with projectionsand depressions is formed on an inside periphery of the joint outer ring51, heat treatment is also applied to the inside periphery of the jointouter ring 51. However, as to the joint outer ring 51, a heat treatmentof the portion 151 with projections and depressions can be applied atthe same time when a heat treatment of the track groove 49 that isoriginally expected to do is made. Therefore, the number of steps for aheat-treatment process does not increase, and rise in heat treatmentcosts is avoided.

In FIG. 29, diameter expansion swaging is made at the bore side of theinboard inner raceway 45; however, as a thirty-second embodiment in FIG.33, diameter expansion swaging can be also made in the region betweenthe double-row raceways 44 and 45. In this case, the dimensions in anaxial direction of both the hub ring 41 and the joint outer ring 51 canbe shortened, so that weight is further lightened.

In a thirty-third embodiment in FIG. 34, diameter expansion swaging ismade in the region between the inner raceways 44 and 45, and the fitportion 148 is disposed more to the inboard side than the position ofthe swaged portion 149, which differs from an embodiment shown in FIG.33. In this case, the fit portion 148 is not necessarily disposed in theregion between the inner raceways 44 and 45, so that the distancebetween the inner raceways 44 and 45 can be shortened than that shown inFIG. 33.

A thirty-fourth embodiment shown in FIG. 35 is an example in which adouble-row tapered-roller bearing is used as a bearing. This type ofbearings has high durability to impact load and particularly suitablefor automobiles that is inherently heavy in weight. In the figure, theswaged portion 149 is disposed on the bore surface of the inner raceway45; however, it can also be disposed in the region between the innerraceways 44 and 45 in the same manner as the embodiment shown in FIG.33, and further, a fit portion 148 can be disposed at the inboard sideof the swaged portion 149 in the same manner as the embodiment shown inFIG. 34.

FIG. 37 shows a bearing device for a driving wheel as a thirty-sixthembodiment. The fit portion 148 that fits to a base portion of theshaft-shaped stem portion 59 of the joint outer ring 51 is formed, andthe serrated portion 58 that fits to the serrated portion 57 of the stemportion 59 of the joint outer ring 51 is formed on a periphery of a boreat the outboard side. A concave portion 201 is formed around theperiphery of a through hole at an outboard end surface of the hub ring41, and a pilot member, or a pilot ring 204, having a wheel guideportion 202 and a brake guide portion 203 is press-fitted into theconcave portion 201. A brake rotor (not shown) is mounted on an outboardflange 200 of the wheel mounting flange 46. Torque transmission isenabled by inserting the stem portion 59 of the joint outer ring 51 intothe through hole of the hub ring 41 with the pilot ring 204 installed onposition, fitting the base portion of the stem portion 59 to the fitportion 148 of the hub ring 41, and at the same time, by fitting theserrated portion 57 to the serrated portion 58 of the hub ring 41.

In the thirty-sixth embodiment, the pilot ring 204 and the hub ring 41are fitted in such a way that the concave portion 201 is provided at theoutboard end surface of the hub ring 41, and the pilot ring 204 isfitted to the concave portion 201. However, it may also be constitutedsuch that, as a thirty-seventh embodiment shown in FIG. 38, a convexportion 205 is provided at the outboard end surface of the hub ring 41,and the pilot ring 204 is fitted to the convex portion 205.

An axial end of the joint outer ring 51 is swaged and plasticallydeformed to be fixed to the pilot ring 204, and the joint outer ring 51is fixed to and unitized with the hub ring 41 through the pilot ring204. Thus, by fixing the joint outer ring 51 to the hub ring 41 byswaging, a shoulder portion of the joint outer ring 51 is butted withthe inboard end portion of the hub ring 41, and thereby pre-load isgiven to the bearing 42.

In the thirty-sixth embodiment, the pilot member 204, a separateelement, is fitted to the outboard end portion of the hub ring 41, axisalignment of the hub ring 41 and the joint outer ring 51 is made throughthe fit portion 148 of the inboard end portion of the hub ring 41 andthe pilot ring 204, and the pilot ring 204 and the hub ring 41 are fixedto be unitized by swaging an axial end of the joint outer ring 51.Because axis alignment of the hub ring 41 and the joint outer ring 51 ismade through the pilot ring 204, a separate element from the hub ring41, run-out of the wheel mounting flange 46 of the hub ring 41 can beprevented. Further, the pilot ring 204 prevents moment load acting onthe hub ring from concentrating on the swaged portion 149.

As described above, by making the pilot ring 204 having the wheel guideportion 202 and the brake guide portion 203 a separate element from thehub ring 41, surface treatments (such as rust-proofing, wax applicationor painting) for the pilot ring 204 may be applied prior to assembling.By doing so, surface treatments for the wheel guide portion 202 and thebrake guide portion 203 that have been carried out in assembly linesbecome unnecessary.

Also, a seal member may be installed on a surface where the pilot ring204 and the hub ring 41 contact with each other. For example, a sealmember may be applied on the surface of either the pilot ring 204 or thehub ring 41, or it may be constituted such that an annular groove 206with sharp bottom corners is formed on the outboard end surface of thehub ring 41, and an O-ring 207 is installed on the groove 206 (see FIG.37 and FIG. 38). The constitution in which the O-ring 207 is installedin the groove 206 may also be applicable to a thirty-eighth andthirty-ninth embodiments that are described below (see FIG. 39 and FIG.40).

Further, a surface-hardened layer may be formed by a heat treatment onthe pilot ring 204. Providing a surface-harden layer on the pilot ring204 can prevent plastic deformation of an outboard end surface of thehub ring 41 induced by swaging. Dip quenching or carburization is suitedas a heat treatment for forming a surface-hardened layer.

In the thirty-sixth embodiment described above, the mouth portion 56 andthe stem portion 59 are unitized to form the joint outer ring 51 of theconstant velocity universal joint 43, and this constitution is alsoapplicable to a bearing device having the joint outer ring 51 in whichthe mouth portion 56 and the stem portion 59 are separable as thethirty-eighth embodiment shown in FIG. 39.

In the thirty-eighth embodiment, a serrated portion 208, as well as anannular groove 210 with sharp bottom corners, is formed on an outsideperiphery of the inboard end portion of the stem portion 59. While on aninside periphery of the outboard end portion of the mouth portion 56, aserrated portion 209 that fits to the serrated portion 208 of the stemportion 59 is formed. The inboard inner raceway 45 formed on theshoulder portion of the joint outer ring 51 in the thirty-sixthembodiment is formed directly on an outside periphery of a shoulderportion of the stem portion 59′ in the thirty-eighth embodiment.

In the thirty-eighth embodiment, the stem portion 59′ and the mouthportion 56 are made detachable in such a way that the mouth portion 56is fitted to the stem portion 59′ through the serrated portions 208 and209 with a fixing ring 211 being installed in the groove 210 of the stemportion 59′. The serrated portions 208 and 209 enable torquetransmission between the stem portion 59′ and the mouth portion 56, anda relative shift in an axial direction between the stem portion 59′ andthe mouth portion 56 is prevented by the fixing ring 211. An end plate212 installed inside the mouth portion 56 prevents grease or othersimilar materials filled in the mouth portion 56 from leaking out.

A bearing device as shown in the thirty-seventh embodiment may also havethe joint outer ring 51 in which the mouth portion 56 and the stemportion 59′ are separable in the same manner as that shown in athirty-ninth embodiment in FIG. 40.

In the thirty-ninth embodiment, the diameter of an inboard end portionof the stem portion 59′ is expanded to integrally form a tubular portion213, a serrated portion 214, as well as an annular groove 216 with sharpbottom corners, is formed on an inside periphery of the tubular portion213. While, on an outside periphery at an outboard end portion of themouth portion 56, a serrated portion 215 that fits to a serrated portion214 of the stem portion 59′ is formed. Also in the thirty-ninthembodiment, the inboard inner raceway 45 that is formed on the shoulderportion of the joint outer ring 51 in the thirty-seventh embodiment isformed directly on an outside periphery of a shoulder of the stemportion 59′.

In the thirty-ninth embodiment, the stem portion 59′ and the mouthportion 56 are made detachable in such a way that the mouth portion 56is fitted to the stem portion 59′ through the serrated portions 214 and215 with a fixing ring 217 being installed in the groove 216 with sharpbottom corners on the tubular portion 213 of the stem portion 59′. Theserrated portions 214 and 215 enable torque transmission between thestem portion 59′ and the mouth portion 56, and a relative shift in anaxial direction between the stem portion 59′ and the mouth portion 56 isprevented by the fixing ring 217. An end plate 218 installed inside themouth portion 56 prevents grease or other similar materials filled inthe mouth portion 56 from leaking.

In the thirty-sixth to thirty-ninth embodiments described above, theposition of the outboard inner raceway of the hub ring 41, or the centerposition of the rolling elements 65 on the inner raceway 44 is definedby ratios described below (see FIG. 41).

That is, {circumflex over (1)} The ratio of a thickness B of the wheelmounting flange to a distance dimension A between an outboardflange-surface 200 of the wheel mounting flange 46 and the position ofan inner raceway is set to B/A≧0.41, {circumflex over (2)} The ratio ofa distance dimension C between a surface on the pilot ring 204 withwhich a swaged portion contacts and the position of the inner raceway tothe distance dimension A between the flange surface 200 and the positionof the inner raceway is set to C/A≧0.79, {circumflex over (3)} The ratioof a curvature R of a sealing portion with which the seal 70 has asliding contact relationship with an outside diameter D of the rollingelement 65 is set to 2R/D≧0.37, {circumflex over (4)} The ratio of thedistance dimension C between a surface on the pilot ring 204 with whichswaged portion contacts and the position of the inner raceway to a pitchcircle diameter PCD of the rolling elements 65 is set to C/PCD≧0.33, and{circumflex over (5)} The ratio of the outside diameter D of the rollingelements 65 to the distance dimension A between the flange surface 200and the position of the inner raceway is set to D/A≧0.45.

The embodiments from the thirty-sixth to the thirty-ninth describedabove have discussed bearing devices having a constitution in which theinboard inner raceway 45 of the double-row inner raceways 44 and 45 isformed directly on the joint outer ring 51 of the constant velocityuniversal joint 43; however, the present invention is not limited tosuch embodiments as described above, and is also applicable to a bearingdevice having a constitution in which an inboard inner raceway is formedon an outside periphery of an inner ring, a separate element, pressedonto a small-diameter stepped portion of a hub ring.

A bearing device of a forty-first embodiment shown in FIG. 42 is, forexample, for a driving wheel, in which the inner ring 75 is fitted ontothe small-diameter stepped portion 74 formed on an outside periphery ofthe hub ring 41, and the inboard inner raceway 45 is formed on anoutside periphery of the inner ring 75. At opening portions of both endsof the bearing 42, there are seal lips slidingly contacting withslingers that are pressed onto outside peripheries of the inner ring 75,a pair of the seals 70 and 71 for sealing an annular space surrounded bythe outer ring, hub ring and the inner ring are fitted into bores atboth ends of the outer ring 62 to prevent leakage of grease filledinside and entry of water or foreign matter from outside.

In the forty-first embodiment, a surface-hardened layer 303 is formed,for example, by induction hardening on an outboard base portion of thewheel mounting flange 46, or on a fillet portion 302 located on a regionextending from the brake rotor mounting surface 200 to the tubular pilotportion 301. Forming the surface-hardened layer 303 facilitatesenhancement of the strength of the outboard base portion, the weakestportion for rotational bending fatigue, while allowing keep currentprocessing methods and facilities, and without changing the shape anddimensions of a wheel mounting flange 46, and without increasing acarbon content or adding strengthening elements to a material.

The surface-hardened layer 303 formed on the fillet portion 302 of thewheel mounting flange 46 is prepared with a surface hardness in therange from HRC 40 through 63, preferably from HRC 58 through 63, withits depth being in the range from 0.3 through 2 mm, preferably from 0.5through 2 mm.

When the surface hardness of the surface-hardened layer 303 is in therange from HRC 40 to 63, preferably from 58 through 63, it effectivelyprevents breakage caused by rotational bending fatigue, becauserotational bending fatigue basically depends on hardness. When surfacehardness is less than HRC 40, desired strength for rotational bendingfatigue is not obtainable.

Preventing breakage caused by rotational bending fatigue meanspreventing production of cracks on a material surface from occurring.Stress caused by rotational bending is highest at the surface, and itreduces toward inside. Therefore, the depth of a surface-hardened layer303 is not necessarily so deep, and a depth from 0.3 through 2 mm,preferably from 0.5 through 2 mm, may be sufficient. Briefly, desiredstrength for rotational bending fatigue is not obtainable when the depthof a surface-hardened layer 303 is less than 0.5 mm, and stress causedby rotational bending reduces at a depth deeper than 2 mm, so that it isnot necessary to make the depth deeper than that described above.

The hub ring 41 and the inner ring 75 are made of carbon steelcontaining C from 0.5 through 0.8 wt %. Carbon steel containing C from0.5 through 0.8 wt % has better workability than SUJ2, high-carbonchrome steel for a bearing (containing C from 0.95 through 1.10 wt %),by a degree corresponding to its less carbon content. A carbon contentof 0.5 wt % or more is needed to increase strength, wear resistance androlling fatigue life, and a content of 0.8 wt % is an upper limit,because processability, machinability, and toughness lower above thisvalue.

In the forty-first embodiment shown in FIG. 42, a surface-hardened layer304 is formed on an outside periphery of the hub ring 41 with which aseal lip of the seal 70 installed at the outboard end portion of theouter ring 62 slidingly contacts, or on a region extending from asealing portion through the inner raceway 44 and to the small-diameterstepped portion 74.

Each portion of the surface-hardened layer 304 is indicated byalphabetical letters from ‘a’ to ‘d’ as follows: portion ‘a’ is asealing portion with which the seal lip of the seal 70 to slidinglycontacts, and wear resistance is required for this portion. By formingthe surface-hardened layer 304 on the sealing portion, strength of thewheel mounting flange 46 is further enhanced. Portion ‘b’ is an innerraceway 44 on which the rolling elements 65 roll, and durability isrequired for this portion. Portion ‘c’ is a part that contacts with theinner ring 75, and portion ‘d’ is a part that fits to the inner ring 75or to the hub ring 41, and therefore, the portion requires resistancefor creeping and fretting.

In a forty-second embodiment shown in FIG. 43, a surface-hardened layer305 is provided on the serrated portion 58 formed on an inside peripheryof the hub ring 41. When the surface-hardened layer 305 is formed on theserrated portion 58 in this way, wear resistance and strength increase,and the increase in strength allows to shorten the effective length ofthe serrated portion 58.

FIG. 44 shows a forty-third embodiment of a bearing device according tothe invention. In the forty-third embodiment, differently from theembodiment shown in FIG. 42 in which the outboard inner raceway 44 isformed directly on the hub ring 41, the inner ring 146 is pressed ontothe small-diameter stepped portion 74 of the hub ring 41 in the samemanner as the inboard inner raceway 45, and the outboard inner raceway44 is formed on an outside periphery of the inner ring 146 which is aseparate element.

In a bearing device of this embodiment, a surface-hardened layer 306 isformed not only on the fillet portion 302 that is an outboard baseportion of the wheel mounting flange 46, but formed also on an inboardbase portion of the wheel mounting flange 46, or on a fillet portion307. By forming the surface-hardened layers 303 and 306 on both sides ofthe base of the wheel mounting flange 46, or about the fillet portions302 and 307, the strength of the wheel mounting flange 46 is furtherincreased.

For a heat treatment method for forming the surface-hardened layers 303to 306, induction hardening is suitable. By effectively usingcharacteristics of induction heating, induction heat treatment as asurface hardening treatment can provide wear resistance or improvedfatigue strength to material, while allowing free selection of thesurface-hardened layers 303 to 306.

Induction heating is a method to make a metal material generate heat inthe material by directly converting electric energy to heat energy usingthe phenomenon of electro-magnetic induction. Induction heat treatmentusing the method of induction heating has many features. Characteristicsof a base material can be maintained even after the treatment, becauseinduction heating enables local heating, facilitates free selection ofthe depth of the layer to be hardened, and allows to control so thatregions other than those to be hardened are not thermally affected.

In the embodiment shown in FIG. 42 and FIG. 44, cases in which the jointouter ring 51 of the constant velocity universal joint 43 is fixed tothe hub ring 41 with the nut 73 are shown; however, the invention is notlimited to such described in the embodiment, and it may also beconstituted such that the joint outer ring 51 is fixed to the hub ring41 by swaging an end portion of the stem portion 59 of the joint outerring 51 to the hub ring 41. Also, the invention is applicable not onlyto a bearing device for a driving wheel, but also to that for a drivenwheel. In a system with which an outer-ring rotates and a wheel mountingflange is provided on a outer ring, a surface-hardened layer is formedon a base portion of the wheel mounting flange on the outer ring.

While there has been described what are at present considered to bepreferred embodiments of the invention, it will be understood thatvarious modifications may be made thereto, and it is intended that theappended claims cover all such modifications as fall within the truespirit and scope of the invention.

1. A wheel bearing device comprising: a hub ring, a constant velocityuniversal joint and a double-row bearing which are unitized together, atleast one of double-row inner raceways of the bearing and a wheelmounting flange being formed on the hub ring, and a stem portion of ajoint outer ring of the constant velocity universal joint being fittedinto the hub ring through torque transmission means, wherein a pilotmember as a separate element having a wheel guide portion and a brakeguide portion is press-fitted to a side-end portion of the wheelmounting flange of the hub ring, and the hub ring and the pilot memberare fixed to the joint outer ring by swaging.
 2. The wheel bearingdevice according to claim 1, wherein the other inner raceway of thedouble-row inner raceways of the bearing is formed directly on the jointouter ring of the constant velocity universal joint.
 3. The wheelbearing device according to claim 1, wherein the hub ring and the pilotmember are unitized by swaging an axial end of the joint outer ring tothe pilot member.
 4. The wheel bearing device comprising: a hub ring, aconstant velocity universal joint and a double-row bearing which areunitized together, at least one of double-row inner raceways of thebearing and a wheel mounting flange being formed on the hub ring, and astem portion of a joint outer ring of the constant velocity universaljoint being fitted into the hub ring through torque transmission means,wherein a pilot member as a separate element having a wheel guideportion and a brake guide portion is fitted to a side-end portion of thewheel mounting flange of the hub ring, and the hub ring and the pilotmember are fixed to the joint outer ring by swaging, and wherein a sealmember is provided on a contact surface between the hub ring and thepilot member.